Abstract: Most software projects evolve interdependently, hence the analysis of software ecosystem has attracted the interest of many researchers. In addition to analyzing some well-known software ecosystems, the software ecosystem in GitHub, together with their features, have also been investigated by researchers in recent years. Unfortunately, the fundamental process of the evolution of software ecosystem in GitHub has not received wide attention nor have the reasons why evolution occurs. In this paper, we conduct an in-depth study on software ecosystem evolution in GitHub. Firstly, we detect the evolving ecosystem in GitHub based on a dynamic community detection method. Then, different evolution events in GitHub are identified and compared. Specifically, we draw a graph to visually show the evolutionary processes of software ecosystem that survived from 2015 to 2018. To understand why an ecosystem survives or dissolves, we perform multiple linear regression analysis and find the important correlating factors of ecosystem survival. Furthermore, we present three case studies to show the typical evolution behaviors of software ecosystem in GitHub.